1. Field of the Invention
Apparatuses and methods consistent with the present invention relate to a broadcasting signal processing apparatus and a control method thereof, and more particularly, to a broadcasting signal processing apparatus, which is capable of reducing a difference in receiving sensitivity between channels which occurs in changing a broadcasting channel when a broadcasting signal is received through a wireless antenna, and a control method thereof.
2. Description of the Related Art
In the related art, a broadcasting signal processing apparatus for allowing a user to select a broadcasting channel and for receiving and/or processing a broadcasting signal corresponding to the selected broadcasting channel includes an antenna for receiving the broadcasting signal, an RF module for selecting a broadcasting frequency corresponding to the selected broadcasting channels from the received broadcasting signal, and a broadcasting signal processor for processing the broadcasting frequency selected in the RF module, that is, a broadcasting signal of the selected broadcasting channel.
In recent years, such a broadcasting signal processing apparatus has a tendency to be provided to receive and/or process broadcasting signals while the broadcasting signal processing apparatus is moving, without being stationary, in order to develop broadcasting systems and meet many desires of users. According to this tendency, broadcasting signal processing apparatuses are equipped with wireless antennas, not wired antennas, to allow the broadcasting signal to be received and/or processed without any restriction on the movement of the broadcasting signal processing apparatus.
A Digital Multimedia Broadcasting (DMB) may be an example of representative broadcastings received and/or processed by the broadcasting signal processing apparatuses equipped with the wireless antennas. At present, the DMB offers seven broadcasting channels from CH 7 to CH 13 using different broadcasting frequency bands. In a related art broadcasting signal processing apparatus equipped with a wireless antenna, the length of the wireless antenna is determined to meet a broadcasting frequency band corresponding to a specified broadcasting channel. For example, the related art broadcasting signal processing apparatus is equipped with a wireless antenna having a length determined to meet a broadcasting frequency band of about 202 MHz to about 209 MHz corresponding to a broadcasting channel CH12.
More specifically, when the length of the wireless antenna in the broadcasting signal processing apparatus is determined to meet the broadcasting channel CH12, the length of the wireless antenna is equal to a half wavelength, i.e., a wavelength (γ)/2, and the wavelength (γ)=propagation velocity (v)/frequency (f). Accordingly, the wavelength (γ) of the broadcasting channel CH12 is about 148 cm (propagation velocity (v=300,000 km/s)/frequency (f=about 202 MHz) and the length of the wireless antenna is determined as about 148 cm/2, i.e., about 74 cm.
However, in addition to the broadcasting channel CH12, the broadcasting signal processing apparatus equipped with the wireless antenna may receive many other broadcasting channels, for example, CH7, CH8, CH9, CH10, CH11 and CH13, using broadcasting frequencies different from the broadcasting frequency of CH12. However, if the related art broadcasting signal processing apparatus equipped with the wireless antenna whose length is determined to meet one broadcasting channel (e.g., CH12) receives a broadcasting signal of a different broadcasting channel (e.g., CH8), since the length of the wireless antenna is determined to meet the broadcasting channel CH12, capability to receive the broadcasting signal of the different broadcasting channel is lowered, which results in a difference in receiving capabilities between broadcasting channels.
Hereinafter, the receiving capability difference between broadcasting channels will be described in brief with reference to FIG. 5. FIG. 5 shows a voltage standing wave ratio (VSWR) a′ in selecting the broadcasting channel CH12 and a VSWR b′ in selecting the broadcasting channel CH8 in the related art broadcasting signal processing apparatus in which the length of the wireless antenna is determined to meet the broadcasting channel CH12. A lower VSWR of an antenna means a higher signal receiving capability. As can be seen from FIG. 5, since the length of the wireless antenna is determined to meet the broadcasting channel CH12, when the wireless antenna receives a broadcasting signal having a broadcasting frequency band (f6˜f7) corresponding to the broadcasting channel CH12, the VSWR a′ of the wireless antenna has a very small value R1. On the other hand, when the wireless antenna receives a broadcasting signal having a different broadcasting frequency band (f2˜f3) corresponding to the broadcasting channel CH8, since the length of the wireless antenna meets the broadcasting channel CH12, not the broadcasting channel CH8, and accordingly, there is no impedance matching between the wireless antenna and the RF module, the VSWR b′ of the antenna has a relatively large value R2.
As mentioned above with reference to FIG. 5, the length of the wireless antenna in the related art broadcasting signal processing apparatus is determined to meet one broadcasting channel (e.g., CH12). Therefore, when broadcasting channels other than the broadcasting channel which has been used to determine the length of the antenna from the broadcasting signal processing apparatus (e.g., CH12) are selected for reproduction of broadcasting, there may arise a problem of irregularity and instability of broadcasting receiving conditions in the absence of impedance matching.